Good question
A lot of pros post on MD..but it's very sanitized there
Get yourself into the majors and I guarantee you'll understand

There is a decent percentage of people in this world who genuinely get a kick out of achieving any interaction they can with someone who has gained notoriety.
A pro would come here, be civil, introduce themselves and within like 20 minutes would have his first (weak) insult.
It happens everywhere. It would be the same on MD, if they allowed it to happen.
This place is only the thunderdome as far as pros go because it's one of the few places where the noise is allowed to be as loud as the genuine talk. Most places elsewhere use a hierarchical system that self moderates the bs away.
If you read twatter, it's the same shit, someone with lots of followers posts, if you actually read the replies to their twats you've got a mixture of people sucking their dick and other people (with essentially the same agenda, albeit a different approach) posting insults.
If I were a premier league football player, I'd fucking love away games. It's fucking hilarious to see the abuse they cop, the moment they get too close to the other supporters. I bet there's some brilliant stuff being laid on them.